1. Field
The present disclosure pertains to the field of microprocessor systems and more specifically to microprocessor systems capable of operating with memory controller over a system bus.
2. Description of Related Art
Dynamic Random Access Memories (DRAMs) may have memory precharge, activate, read, and write operations. In particular, a memory controller that addresses a bank of memory must first precharge the memory bank, then the addressed page within the bank must be activated before the addressed column in that page is accessed (read or written). Accesses to an open DRAM page (a “page hit”) indicates the memory being accessed has already been precharged and activated. Data may be read to or written from the DRAM page without having to precharge or activate the memory during each memory access. When a “page miss” occurs (i.e., data is accessed from a page in memory other than from the page that is open), the currently-open page must be closed (i.e., written back to the DRAM chip from the sense amps)before the new memory page can be precharged and activated to enable accessing. Writing the old page to DRAM and precharging and activating the new DRAM pages takes time and memory command bus bandwidth, which in turn increases the access latency of the memory access, resulting in an inefficient use of the memory bus (reduced bandwidth utilization) and a loss in performance of an apparatus (e.g., a computer) employing DRAM.